It is commonplace for digital integrated circuits to operate at higher frequencies that can create parasitic impedances for the various circuit elements. As the operating frequencies increase, the effects of parasitic impedances of the capacitors should often be considered when fine-tuning or designing a circuit or system. The effects of equivalent series resistance (ESR) and equivalent series inductance (ESL) in a typical digital application should be considered to properly predict circuit performance in design because the ESR and ESL of chip capacitors can dramatically alter the voltage drops across the integrated circuit (IC). The use of capacitors in digital circuitry is not new, but as microprocessor clock speeds increase, the parasitic effects of capacitors within integrated circuits (ICs) become more important.
As the ESR of a device increases, an increase in the ripple voltage for a given parasitic impedance of a capacitor. Additionally, increases in ESR can create unwanted voltage drops that affect circuit operation. Parasitic inductance also affects circuit operation by adding unwanted noise and undesired voltage drops. An increase in inductance results in an increase in the ripple voltage from switching and an increase in undesired voltage drops that should be accounted for in circuit design. Accounting for parasitic impedances (resistance and inductance) of a capacitor can be difficult especially when a fast response is needed in a feedback loop to support high frequency operations. While there are existing systems and/or circuit designs that provide fast feedback despite the parasitic impedances, such solutions are often complex and consume integrated circuit real estate and power.
The use of the same reference symbols in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.